Investigators from Vietnam's highest office of prosecutors have concluded that a man who died in a police station in the southern province of Binh Duong last April committed suicide and was not was beaten to death as suspected.

They have also deemed illegal his detention by the police.

A Tuoi Tre report Thursday said the People's Supreme Procuracy has found that Nguyen Cong Nhut, 30, killed himself out of "regret" for making mistakes during his work at the Kumho Tire Factory, allowing some people to steal tires, and because he was afraid of going to prison.

Tests carried out by agencies under the Ministry of Defense have shown that Nhut was not tortured and confirmed that the suicide note was written by him, the prosecutor's office said.

Nhut was found dead at the Ben Cat District police station on August 25 last year, four days after he was summoned for interrogation over the theft of 50 tires at the Kumho factory.

Police had then claimed he had hung himself with the cord of a mobile phone charger, and produced a suicide note.

According to the People's Supreme Procuracy, the arrest was illegal because local police had not informed the district People's Procuracy and did not have an arrest warrant.

The investigators have proposed that leaders of Binh Duong police department review the wrongdoings of involved people and punish them strictly, the newspaper reported.

After Nhut's death, his wife Nguyen Thi Thanh Tuyen and his family filed several petitions with local authorities asking for further investigations. They suspected his death was caused by police beating.

During the investigations, Tuyen also accused Nguyen Thanh Phu, one of the investigators in the theft, of asking her for to have sex with him in exchange for helping her husband. She released tapes and voice recordings of her conversations with Phu.

Phu, who told the provincial police that he was just "joking" when soliciting sex from Tuyen, was later demoted from major to captain.